Wireless telephone communication has become a leading growth industry in the late twentieth century. Innovations in electronics have made such communication inexpensive enough for many to afford. One such system for wireless telephony is specified by the U.K. Cordless Telephone, Second Generation (CT-2) standard. CT-2 specifies such functions as how the analog signals from a cordless telephone handset are digitized, encoded, and modulated by a radio frequency (RF) carrier to be transmitted to a base station. A CT-2 telephone handset receives an analog voice signal from a microphone. The voice signal is converted to PCM, processed through an ADPCM encoder (which conforms to CCITT Recommendation G.721), and then modulated and transmitted (along with other signalling information) according to the CT-2 Common Air Interface (CAI) standard to a base station. Transmit and receive signals are sent and received to and from the base station in packets in a half-duplex fashion. For signal reception, a packet is received, demodulated, processed through a G.721 ADPCM decoder, converted from digital PCM to analog, and then provided to a speaker.
In order for CT-2 cordless telephones to be affordable by a large number of people, it is necessary to minimize the cost of the handset. Modern electronics has made several of the functions required by the CT-2 handset available through inexpensive integrated circuits. For example, the Motorola MC14410 2-of-8 Tone Encoder, the Motorola MC145532 ADPCM Transcoder, and either the Motorola MC145554 .mu.-law PCM Codec-Filter or the Motorola MC145557 A-law PCM Codec-Filter may be used to implement a substantial part of the function of a CT-2 handset. These commercial integrated circuits provide an inexpensive, highly integrated telephone handset. However, as time goes on further cost reductions are necessary in order to make the CT-2 system attractive to more and more consumers.